Femoral head arthroplasty system

ABSTRACT

A femoral head arthroplasty system can comprise a femoral prosthesis comprising a mounting plate having a first side and an opposed second side. An adapter can extend from the second side of the mounting plate. An implant body can extend from the first side of the mounting plate. The implant body can extend from the mounting plate by a distance no greater than 90 mm. The femoral head arthroplasty system can further comprise a femoral head replacement having a generally spherical surface and comprising a recess that is shaped to complementarily receive the adapter of the femoral prosthesis.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of U.S. ProvisionalPatent Application No. 62/860,549, filed Jun. 12, 2019, the entirety ofwhich is hereby incorporated by reference herein.

FIELD

The disclosed invention relates to hip implants, and, more particularly,to systems for securing a femoral head replacement to the femur of asubject.

BACKGROUND

Conventional hip implants are inserted into the femur about five to sixinches. The use of such conventional hip implants requires removal of asignificant quantity of a patient's bone, which can be undesirable.There is a need for hip implant systems that eliminate the need forremoval of such significant quantities of bone.

SUMMARY

Described herein, in various aspects, is a femoral head arthroplastysystem. The femoral head arthroplasty system can comprise a femoralprosthesis. The femoral prosthesis can comprise a mounting plate havinga first side and an opposed second side, an adapter extending from thesecond side of the mounting plate, and an implant body extending fromthe first side of the mounting plate. The implant body can extend fromthe mounting plate by a distance no greater than 90 mm. A femoral headreplacement can have a generally spherical surface and can comprise arecess that is shaped to complementarily receive the adapter of thefemoral prosthesis.

A femoral head arthroplasty system can comprise a femoral prosthesis.The femoral prosthesis can comprise a mounting plate having a first sideand an opposed second side, an adapter extending from the second side ofthe mounting plate, and an implant body extending from the first side ofthe mounting plate, wherein a distal end of the implant body has aplanar face that is generally parallel to the mounting plate. A femoralhead replacement can have a generally spherical surface and can comprisea recess that is shaped to complementarily receive the adapter of thefemoral prosthesis.

A femoral head arthroplasty system can comprise a femoral prosthesis.The femoral prosthesis can comprise a mounting plate having a first sideand an opposed second side. An implant body can extend from the firstside of the mounting plate. The implant body can extend from themounting plate by a distance no greater than 90 mm. The mounting plateand the implant body can cooperate to define a recess. A femoral headreplacement can have a generally spherical portion and an adapterextending distally from the generally spherical portion. The adapter canbe configured for complementary receipt within the recess of the femoralprosthesis.

The implant body can comprise at least one radially extending spline.

The implant body can comprise a plurality of radially extending splines.

The implant body can comprise a generally cylindrical portion.

The implant body can define a hemi-cylindrical surface.

The implant body can comprise mounting hardware. The mounting plate candefine at least one opening configured to receive the mounting hardware.

The mounting hardware can comprise at least one screw.

The femoral prosthesis can comprise a porous or textured metal.

The porous or textured metal can be at least one metal selected from thegroup consisting of cobalt chromium, titanium, and tantalum.

The femoral prosthesis can comprise a coating.

The coating can be one selected from the group consisting ofhydroxyapatite, titanium oxide, titanium nitride, zirconium oxide, andpyrolytic carbon.

The coating can be configured to promote ingrowth or on-growth of bone.

The diameter of at least a portion of the implant body can range fromabout 10 mm to about 18 mm.

The implant body can have a variable outer diameter.

The adapter can have a Morse taper.

The femoral head replacement can be angularly offset from the femoralprosthesis.

A method can comprise: forming a prepared site within a femur; andimplanting a femoral head arthroplasty system such that the implant bodyis received within the prepared site, wherein the prepared site extendsno more than 30 mm distal to the lesser trochanter of the femur.

The mounting plate can have a major dimension that is greater than orequal to a major radial dimension of the femur. The mounting plate canabut cortical bone at a cut proximal end of the femur.

A kit can comprise: a femoral prosthesis comprising: a mounting platehaving an first side and an opposed second side, an adapter extendingfrom the second side of the mounting plate, and an implant bodyextending from the first side of the mounting plate, wherein the implantbody extends from the mounting plate by a distance no greater than 90mm. The kit can further comprise a plurality of femoral headreplacements, each femoral head replacement having a generally sphericalsurface and comprising a recess that is shaped to complementarilyreceive the adapter of the femoral prosthesis, wherein each femoral headreplacement of the plurality of femoral head replacements differs fromevery other femoral head replacement of the plurality of femoral headreplacements in size or material.

Additional advantages of the invention will be set forth in part in thedescription that follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. Theadvantages of the invention will be realized and attained by means ofthe elements and combinations particularly pointed out in the appendedclaims. It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory only and are not restrictive of the invention, as claimed.

DESCRIPTION OF THE DRAWINGS

These and other features of the preferred embodiments of the inventionwill become more apparent in the detailed description in which referenceis made to the appended drawings wherein:

FIG. 1 is a side view of a femoral prosthesis of a femoral headarthroplasty system, in accordance with embodiments disclosed herein.

FIG. 2 is the side view of the femoral prosthesis of FIG. 1 withdimensions for one exemplary embodiment.

FIG. 3 is a front view of the femoral prosthesis of FIG. 1.

FIG. 4 is the front view of the femoral prosthesis of FIG. 3 withdimensions for one exemplary embodiment.

FIG. 5 is a rear view of the femoral prosthesis of FIG. 1.

FIG. 6 is the rear view of the femoral prosthesis of FIG. 5 withdimensions for one exemplary embodiment.

FIG. 7 is a side view of a femoral head replacement of the femoral headarthroplasty system for use with the femoral prosthesis of FIG. 1.

FIG. 8 is a side view of another embodiment of a femoral headarthroplasty system.

FIG. 9 is a partial cutaway view of a femoral head arthroplasty systeminstalled in a femur.

FIG. 10 is a rear perspective view of an exemplary femoral prosthesis inaccordance with embodiments disclosed herein.

FIG. 11 is a front perspective view of the exemplary femoral prosthesisof FIG. 10.

FIG. 12 is a front view of the exemplary femoral prosthesis of FIG. 10.

FIG. 13 is a top view of the exemplary femoral prosthesis of FIG. 10.

FIG. 14 is a side view of the exemplary femoral prosthesis of FIG. 10.

FIG. 15 is a perspective view of an exemplary femoral prosthesis inaccordance with embodiments disclosed herein.

FIG. 16 is a cross sectional view of the exemplary femoral prosthesis ofFIG. 15.

FIG. 17 is a side view of a fixation screw for use with the femoralprosthesis.

FIG. 18 is a first end view of the fixation screw of FIG. 17.

FIG. 19 is a cross sectional view of the screw taken in the plane A-A ofFIG. 18.

FIG. 20 is a detail view of the cross sectional view of the screw inFIG. 19 within the circle B.

FIG. 21 is a detail view of the cross sectional view of the screw inFIG. 19 within the circle C.

FIG. 22 is a second end view of the fixation screw of FIG. 17.

It should be understood that any dimensions or other measurementsindicated within the figures are merely exemplary and that otherdimensions and measurements are contemplated.

DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the invention, are shown. Indeed, this invention may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout. It is tobe understood that this invention is not limited to the particularmethodology and protocols described, as such may vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to limit thescope of the present invention.

Many modifications and other embodiments of the invention set forthherein will come to mind to one skilled in the art to which theinvention pertains having the benefit of the teachings presented in theforegoing description and the associated drawings. Therefore, it is tobe understood that the invention is not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

As used herein the singular forms “a,” “an,” and “the” include pluralreferents unless the context clearly dictates otherwise. For example,use of the term “a screw” can refer to one or more of such screws, andso forth.

All technical and scientific terms used herein have the same meaning ascommonly understood to one of ordinary skill in the art to which thisinvention belongs unless clearly indicated otherwise.

As used herein, the terms “optional” or “optionally” mean that thesubsequently described event or circumstance may or may not occur, andthat the description includes instances where said event or circumstanceoccurs and instances where it does not.

As used herein, the term “at least one of” is intended to be synonymouswith “one or more of” For example, “at least one of A, B and C”explicitly includes only A, only B, only C, and combinations of each.

The word “or” as used herein means any one member of a particular listand also includes any combination of members of that list.

Ranges can be expressed herein as from “about” one particular value,and/or to “about” another particular value. When such a range isexpressed, another aspect includes from the one particular value and/orto the other particular value. Similarly, when values are expressed asapproximations, by use of the antecedent “about,” it will be understoodthat the particular value forms another aspect. It will be furtherunderstood that the endpoints of each of the ranges are significant bothin relation to the other endpoint, and independently of the otherendpoint. Optionally, in some aspects, when values are approximated byuse of the antecedent “about,” it is contemplated that values within upto 15%, up to 10%, up to 5%, or up to 1% (above or below) of theparticularly stated value can be included within the scope of thoseaspects. Similarly, in some aspects, when values or characteristics areapproximated by the use of the antecedent “approximately,” “generally,”or “substantially,” it is contemplated that values within up to 15%, upto 10%, up to 5%, or up to 1% (above or below) of the particularlystated value or characteristic can be included within the scope of thoseaspects.

As used herein, the term “patient” can refer to a human or an animalthat receives an implant as further disclosed herein. In exemplaryaspects, a patient can be a human who has been determined to be in needof receiving an implant as disclosed herein.

It is to be understood that unless otherwise expressly stated, it is inno way intended that any method set forth herein be construed asrequiring that its steps be performed in a specific order. Accordingly,where a method claim does not actually recite an order to be followed byits steps or it is not otherwise specifically stated in the claims ordescriptions that the steps are to be limited to a specific order, it isin no way intended that an order be inferred, in any respect. This holdsfor any possible non-express basis for interpretation, including:matters of logic with respect to arrangement of steps or operationalflow; plain meaning derived from grammatical organization orpunctuation; and the number or type of aspects described in thespecification.

The following description supplies specific details in order to providea thorough understanding. Nevertheless, the skilled artisan wouldunderstand that the apparatus, system, and associated methods of usingthe apparatus can be implemented and used without employing thesespecific details. Indeed, the apparatus, system, and associated methodscan be placed into practice by modifying the illustrated apparatus,system, and associated methods and can be used in conjunction with anyother apparatus and techniques conventionally used in the industry.

Disclosed herein, in various aspects and with reference to FIG. 1, is afemoral prosthesis 100 of a femoral head arthroplasty system. Thefemoral prosthesis 100 can comprise a mounting plate 110 having a firstside 112 and an opposing second side 114. The mounting plate 110 canhave a planar or substantially planar profile and a thickness 502between about three and about seven millimeters (e.g., about fivemillimeters) in a first dimension (measured along a first axis 302) thatis perpendicular to the first side's surface. The mounting plate 110 canextend about twenty-five to about forty millimeters (e.g., aboutthirty-four millimeters) in a second dimension (measured along a secondaxis 304) and a length 504 of about sixteen to about twenty fivemillimeters (e.g., about twenty-two millimeters) in a third dimension(measured along a third axis 306). The femoral prosthesis's mountingplate 110 can have a major dimension that is greater than the majorradial dimension of the patient's femur so that, when implanted withinthe femur, the mounting plate abuts the femur's outer radial wall. Apair of top corners can define a radius r1 (optionally, of about twomillimeters), and a bottom of the mounting plate 110 can define acontinuous arcuate profile (optionally, having a radius of elevenmillimeters, or about half of the width of the mounting plate measuredalong the third axis 306).

The mounting plate 110 can define one or more through-holes 120 (e.g., apair, as shown) that can receive mounting hardware for attaching thefemoral prosthesis to a patient. The holes 122 can have respectivediameters d5 (optionally, a diameter ranging from about 4 millimeters toabout 10 millimeters, or more preferably, being about sevenmillimeters). In some aspects, the holes 122 can be spaced fromrespective side edges of the mounting plate by distances 526 (e.g., atleast one millimeter, between one and 4 millimeters, or, morepreferably, about two millimeters). The pair of through holes 120 canoptionally define female threads 122 therein for receiving male threadsof mounting screws (see also FIGS. 15 and 16). In some optional aspects,the pair of through holes 120 can be centered along the third axis 306so that the femoral prosthesis is symmetrical about a plane that extendsin the first and third dimensions (containing axes 302, 306) and bisectsthe femoral prosthesis 100. Although embodiments described hereincomprise features for attachment via screws, in further embodiments,other attachment means, such as wires, sutures, or cables, may be used.

An implant body 130 can extend from the first side 112 of the mountingplate 110. The implant body 130 can be disposed below (i.e., offset inthe second dimension (along second axis 304) from) the pair ofthrough-holes 120. The implant body 130 can comprise a first cylindricalor generally cylindrical protrusion 132 that extends perpendicularly tothe face of the mounting plate's first side 112. The first generallycylindrical protrusion 132 can extend less than ninety and greater thantwenty millimeters, and optionally less than seventy-five and greaterthan thirty millimeters or between thirty-five and sixty millimeters,(e.g., about forty millimeters or about forty-five millimeters) from thefirst side 112 of the mounting plate along a first axis 134. The firstgenerally cylindrical protrusion 132 can optionally have a diameter d1between about ten and about eighteen millimeters (e.g., about fourteenmillimeters). A distal end of the first generally cylindrical protrusion132 (i.e., the end farthest away from the mounting plate 110) can havean arcuate edge 136 that extends a length 512 in the first dimension 302ranging from about three millimeters to about eight millimeters, or morepreferably, being about five millimeters. The distal end of the firstgenerally cylindrical protrusion 132 can optionally have a planar face138 that is generally parallel to the mounting plate. The firstgenerally cylindrical protrusion 132 can be spaced from the bottom ofthe mounting plate 110, for example by about two millimeters. The firstaxis 134 of the first generally cylindrical protrusion 132 canoptionally be spaced from the bottom of the mounting plate by a distance530 (e.g., optionally, from about seven millimeters to about 12millimeters, or about nine millimeters). In some optional aspects, thefirst generally cylindrical protrusion 132 can be spaced from the lowerend of the mounting plate by a distance 506 (e.g., optionally, fromabout one millimeter to about four millimeters, or about twomillimeters).

The implant body 130 can further comprise a second cylindrical orgenerally cylindrical protrusion 150 that extends along a second axis152 that is parallel to the first axis 134. The second axis 152 canoptionally be directly vertically above the first axis 134. The secondgenerally cylindrical portion 150 can extend a length 508 about ten toabout forty millimeters (e.g., from about ten millimeters to abouttwenty millimeters, or about fifteen millimeters) from the first side112 of the mounting plate 110. The second generally cylindrical portion150 can therefore have an end opposite the mounting plate 110 that is alength 516 (e.g., from about 25 millimeters to about 35 millimeters, orabout thirty millimeters) from the end of the first generallycylindrical portion 130 opposite the mounting plate. The first andsecond axes 134, 152 can be spaced by less than the sum of therespective radiuses of the first and second generally cylindricalportions so that the second generally cylindrical protrusion 150overlaps the first generally cylindrical protrusion 132. Accordingly, ina cross sectional plane perpendicular to the first axis 134, theoverlapping first and second generally cylindrical protrusions 132, 150can have a figure-eight shape. Optionally, the second axis 152 canextend along a top edge of the first generally cylindrical protrusion132. The second axis 152 can be spaced from the top of the mountingplate by a distance 532 (e.g., optionally, from about 15 millimeters toabout 20 millimeters, or about eighteen millimeters) and can be spacedfrom the bottom of the mounting plate by a distance 534 (e.g.,optionally, from about 13 millimeters to about 18 millimeters, or aboutsixteen millimeters). That is, the second axis 152 can be spaced fromthe first axis by the radius of the first generally cylindricalprotrusion 132. The second generally cylindrical protrusion 150 can havea radius r3 of about five to about nine millimeters (e.g., about sevenmillimeters). The first and second generally cylindrical protrusions132, 150 can cooperate to provide an oblong cross section so that theimplant body 130 is inhibited from rotation. Moreover, the combinedcross sectional shape of the first and second generally cylindricalprotrusions (e.g., a figure-eight shape) can cooperate with a bonepreparation site that is easily prepared by a surgeon. In furtherembodiments, the implant body 130 can have various other cross sectionalprofiles in planes perpendicular to the implant body's longitudinaldimension, including a generally cylindrical profile, an oval profile, apolygonal profile (e.g., a square or rectangular profile), or an oblongprofile.

Optionally, the implant body 130 can extend from the mounting plate by adistance of no greater than ninety millimeters, or no greater thanseventy-five millimeters, or no greater than sixty millimeters, or nogreater than fifty millimeters, or no greater than forty-fivemillimeters. As further disclosed herein, it is contemplated that theminimal length of the implant body 130 can reduce the amount of nativebone of a subject that must be removed to accommodate the implant body.

An adapter 160 can extend from, and be oriented perpendicularly orsubstantially perpendicularly to, the second side 114 of the mountingplate 110. The adapter 160 can optionally have a central axis 161 thatis collinear with the second axis 152. Accordingly, the adapter 160 canbe superiorly axially offset from (i.e. above) the axis 134 of the firstgenerally cylindrical protrusion 132. In this way, for some patients, afemoral head attached to the adapter 160 can most accurately recreatethe patient's normal anatomy. In further embodiments, the adapter canhave an axis offset from the axis 152. Optionally, in some suchembodiments, the adapter 160 can be axially aligned with the axis 134.The adapter 160 can comprise a frustoconical portion 162 that attaches,via a neck portion 164, to the mounting plate 110. The neck portion canhave a length 514 of from about three millimeters to about sevenmillimeters, or of about five millimeters. The frustoconical portion 162can taper from a proximal end 166 to a distal end 168 (moving away fromthe mounting plate 110). The frustoconical portion 162 can optionallyhave a Morse taper. The proximal end 166 can optionally have a diameterd2 of about twelve to about sixteen millimeters (e.g., about fourteenmillimeters), and the distal end 168 can optionally have a diameter d3of about ten millimeters to about fourteen millimeters (e.g., abouttwelve millimeters). The frustoconical portion 162 can extend axially alength 510 of about ten to about eighteen millimeters (e.g., aboutfourteen millimeters) from the proximal end 166 to the distal end 168.In some aspects, the adapter's central axis can be spaced from the topof the mounting plate by a length 520 (optionally, from about 15millimeters to about 20 millimeters, or about eighteen millimeters) andspaced from the bottom of the mounting plate by a length 522(optionally, from about 13 millimeters to about 18 millimeters, or ofsixteen millimeters). The adapter's radial-most surface can be spacedfrom the respective opposing side edges of the mounting plate in thethird dimension 306 by a distance 524 (optionally, from about threemillimeters to about six millimeters, or of about four millimeters).Optionally, at least a portion of the frustoconical portion'scircumferential surface can comprise a texture. Said texture can improvefrictional engagement between the adapter 160 and the femoral headreplacement. In some optional aspects, a helical groove having a pitchof 0.5 millimeters can define said texture.

The neck portion 164 of the adapter 160 can have a cross section thatvaries along its axis in an arcuate profile. At a halfway point alongits axis, the neck portion 164 can have a minimum diameter d4, which, insome embodiments, can be about twelve millimeters. Opposing ends of theneck portion 164 can each have a diameter d2 of about fourteenmillimeters. Accordingly, the minimum diameter can be about twomillimeters less than the maximum diameter of the neck portion 154. Theneck portion's narrowing diameter can provide a location to grip thefemoral prosthesis during implantation and removal of the femoralprosthesis.

Although shown extending parallel to the implant body 130, in furtherembodiments, the adapter 160 can extend at various angles with respectto the implant body 130 in order to vary the varus/valgus angle of thefemoral head with respect to the longitudinal dimension of the femur.

Referring to FIG. 7, the adapter 160 can receive a femoral headreplacement 200. The femoral head replacement 200 can have a shape thatcooperates with a hip socket of the patient's pelvis or an artificialhip socket. In some embodiments, the femoral head replacement 200 canhave the shape of a natural femoral head. The femoral head replacement200 can have a generally spherical profile. The femoral head replacement200 can define a recess 210. The recess 210 can have a complementaryshape to the adapter 160 (FIG. 1) of the femoral prosthesis 100 (FIG.1). For example, the recess 210 can have a frustoconical profile. Theprosthesis 200 can optionally be a conventional component known to thoseskilled in the art.

The femoral prosthesis 100 can couple to the femoral head replacement200 to create a femoral head arthroplasty system 250. In someembodiments, the femoral prosthesis 100 and the femoral head replacement200 can couple permanently, while in further embodiments, the pair cancouple via a non-permanent means. The adapter 160 and femoral headreplacement 200 can have an interference fit (e.g., via a Morse taper)so that the respective components frictionally engage each other. Asstated above, at least one of the adapter 160 and the femoral headreplacement 200 can optionally have a texture (i.e., surface texture) toimprove the engagement between the respective components.

Referring to FIG. 8, in further embodiments, a femoral head replacement200′ can comprise a generally spherical portion 202′ and an adapter 160′that extends distally from the generally spherical portion 202′. Afemoral prosthesis 100′ can comprise a recess 210′ and can otherwisehave the same shape and dimensions as that of the femoral prosthesis 100(FIG. 1). Although shown as a frustoconical protrusion, the adapter 160′and recess 210′ can have profiles similar to that of the adapter 160(FIG. 1) and the recess 210 (FIG. 7), respectively, or any other adapterprofile known to those skilled in the art.

In some embodiments, the femoral prosthesis can comprise at least oneradially extending spline 180 or, as shown, a plurality of radiallyextending splines 180. The radially extending spline(s) 180 can providesurfaces against which bone can grow as well as inhibit rotation of thefemoral prosthesis about its axis of elongation.

The femoral prosthesis 100 and/or the femoral head replacement 200 cancomprise various materials known to those skilled in the art, such as,for example, porous, coated titanium, ceramics, tantalum, cobaltchromium alloy, or various other porous metals. The material(s) can beporous or textured in order to allow bone in-growth or on-growth. Thematerial(s) can be strong enough to bear the weight of the patientwithout fracturing.

The femoral prosthesis 100 and/or the femoral head replacement 200 cancomprise a coating. Said coating can comprise one or more of thefollowing: hydroxyapatite, titanium oxide, titanium nitride, zirconiumoxide, and pyrolytic carbon. In further embodiments, the coating cancomprise gold, ceramics, polymers (e.g., ultra-high molecular weightpolyethylene), diamond-like carbon (DLC) coatings, oxidized zirconium,titanium nitride or various other coatings known to those skilled in theart. The coating(s) can optionally be low friction and can optionally behydrophobic.

Referring to FIGS. 10-14, in some aspects, the implant body 130 of theprosthesis 100 can have an elongate profile in the second dimension(along the second axis 304). That is, in cross sections perpendicular tothe second axis 304, the implant body 130 can have a major dimensionmeasured along the second axis 304 and a minor dimension measured alongthe third axis 306. For example, the implant body 130 can define twohemi-cylindrical surfaces 190 that are spaced along the second axis 304and connected via planar faces 192. This or another non-axiallysymmetric profile can inhibit rotation of the implant body relative tothe femur. In some aspects, the implant body can have a major dimensionof between 18 and 25 millimeters (e.g., about 21 millimeters) measuredalong the second axis 304 and a minor dimension of between 12 and 18(e.g., about 14 millimeters) measured along the third axis 306.

In some optional aspects, the centerline 194 of the implant body (i.e.,the line extending through the centroid of the cross sections in planesperpendicular to the first dimension (first axis 302)) can be collinearwith the central axis 161 of the adapter 160. In further optionalaspects, as shown in FIGS. 15 and 16, the centerline 194 can be offsetfrom the central axis 161 of the adapter 160 (optionally, offset fromthe central axis 161 in the second dimension (relative to the secondaxis 304)).

In some optional aspects, the distal end of the implant body 130 canoptionally have a planar face 138 that is parallel or generally parallelto the mounting plate. In further aspects, it is contemplated that thedistal end of the implant body can define a rounded, oblong surface 139or other non-planar surface that extends parallel to the mounting plate.For example, the implant body 130 can define first and second radii 141(optionally, spherical surfaces) that are spaced relative to each otheralong the second dimension 304 (and that are measured in a planecontaining the first and second axes).

In some aspects, the centerline 194 of the implant body can extendperpendicularly to the mounting plate 110 along an entire length of theimplant body. For example, within any plane that intersects the implantbody and is perpendicular to the first axis 302, a center point (whichcan optionally correspond to a center of mass) of the portion of theimplant body within the plane will be intersected by the centerline 194.In further aspects, it is contemplated that the apparatus can besymmetric about a plane that is perpendicular to the second dimension304 and bisects the implant body (and, therefore, includes thecenterline 194). Optionally, in still further aspects, it iscontemplated that the implant body can be symmetric about both (a) afirst plane that is perpendicular to the second dimension 304 andbisects the implant body; and (b) a second plane that is perpendicularto the third dimension 306 and bisects the implant body. It iscontemplated that the above-described configurations, by avoiding theneed for providing an angled or asymmetric implant body (for example, asmight be necessary to permit deeper advancement of an implant bodywithin a native bone), can provide advantageous balance and forcetransmission properties while minimizing the amount of bone that isremoved from the patient to accommodate the implant body.

Referring to FIGS. 10-14, it is further contemplated that in someaspects, the neck portion 164 can have a constant diameter (instead ofthe narrowing diameter as depicted in FIG. 1) to increase the strengthof the prosthesis.

Referring to FIGS. 17-22, a fixation screw 240 can have a head 241defining a first thread (or plurality of threads) 242 and a body 243defining a second thread (or plurality of threads) 244. Optionally, thehead of the screw can define a taper. Accordingly, the hole 120 (FIG.16) can define a corresponding taper. The fixation screw can compriseone or more (e.g., optionally, three equally circumferentially spaced)self-tapping features 246 for tapping the bone during insertion of thescrew. The fixation screw can further comprise one or more (e.g.,optionally, three equally circumferentially spaced) self-tappingfeatures 247 for tapping the bone during removal of the screw. It shouldbe understood that the dimensions (in millimeters) provided in thefigures should be understood to be optional aspects.

It is further contemplated that the prosthesis can be fixated to thefemur, additionally or alternatively, with bone ingrowth and/or ongrowthand/or cemented fixation.

A kit can comprise a femoral prosthesis 100 and a plurality of femoralhead replacements 200. Each of femoral head replacements 200 can differfrom the others in at least one of size or material.

Referring to FIG. 9, a medical professional (e.g., an orthopedicsurgeon) can form a prepared site within a femur 400. For example, themedical professional can cut off a portion of the patient's naturalfemoral head. Optionally, the surgeon can use a patient-specific cuttingguide that locates the optimal location and angle for removing thefemoral head. According to one embodiment, the cutting guide cancomprise a frame that defines a slot for guiding a cutting saw. Thecutting guide can temporarily be fastened to the femur using pins orscrews and subsequently be removed from the femur after cutting. Thesurgeon can drill/ream a pair of overlapping holes to receive the firstand second cylindrical portions 132, 150. In further aspects, theoverlapping holes can further be bored to provide an opening to receivethe implant body 130 (e.g., for the embodiments shown in FIGS. 10-14).The prepared site can be positioned further proximally along the neck ofthe femur (toward the original femoral head) than prepared sites ofconventional femoral prostheses for hip replacement. The prepared sitecan optionally extend no more than thirty millimeters distal to thelesser trochanter 402 of the femur 400 (i.e., past the lesser trochanteralong femoral shaft's longitudinal axis in the direction toward thepatient's foot). The medical professional can then implant the femoralprosthesis so that the implant body is received within the preparedsite. The femoral prosthesis can be inserted so that the mounting plateabuts a superior end of the femur. The medical professional can drillholes in the patient's bone for receiving the screws or other fasteners.Screws 240 or other fasteners can be used to secure the femoralprosthesis in place. Optionally, the surgeon can drill holes into thefemur to receive screws 240. The femoral head replacement can then beattached to the femoral prosthesis.

Compared to conventional implants, embodiments disclosed herein canenable hip implants that require less bone removal. That is, a shortersegment of bone can be removed, leaving a portion of the femoral neckthrough which the femoral prosthesis can extend. The disclosedembodiments can reduce blood loss during surgery and enable easierinsertion for the surgeon, particularly in cases of anterior approachsurgery. The disclosed embodiments can be associated with smallerincisions than conventional implants and can provide for easier re-dosurgery if need arises.

EXEMPLARY ASPECTS

In view of the described products, systems, and methods and variationsthereof, herein below are described certain more particularly describedaspects of the invention. These particularly recited aspects should nothowever be interpreted to have any limiting effect on any differentclaims containing different or more general teachings described herein,or that the “particular” aspects are somehow limited in some way otherthan the inherent meanings of the language literally used therein.

Aspect 1: A femoral head arthroplasty system comprising: a femoralprosthesis comprising: a mounting plate having a first side and anopposed second side, an adapter extending from the second side of themounting plate, and an implant body extending from the first side of themounting plate, wherein the implant body extends from the mounting plateby a distance no greater than 90 mm; and a femoral head replacementhaving a generally spherical surface and comprising a recess that isshaped to complementarily receive the adapter of the femoral prosthesis.

Aspect 2: A femoral head arthroplasty system comprising: a femoralprosthesis comprising: a mounting plate having a first side and anopposed second side, an adapter extending from the second side of themounting plate, an implant body extending from the first side of themounting plate, wherein the implant body has a distal end, wherein thedistal end of the body defines a surface that extends generally parallelto the mounting plate; and a femoral head replacement comprising arecess that is shaped to complementarily receive the adapter of thefemoral prosthesis.

Aspect 3: A femoral head arthroplasty system comprising: a femoralprosthesis comprising: a mounting plate having a first side and anopposed second side; and an implant body extending from the first sideof the mounting plate, wherein the implant body extends from themounting plate by a distance no greater than 90 mm, wherein the mountingplate and the implant body cooperate to define a recess; and a femoralhead replacement having a generally spherical portion and an adapterextending distally from the generally spherical portion, wherein theadapter is configured for complementary receipt within the recess of thefemoral prosthesis.

Aspect 4: The femoral head arthroplasty system of aspects 1-3, whereinthe implant body comprises at least one radially extending spline.

Aspect 5: The femoral head arthroplasty system of aspect 4, wherein theimplant body comprises a plurality of radially extending splines.

Aspect 6: The femoral head arthroplasty system of any of aspect 1-3,wherein the implant body defines a generally hemicylindrical surface.

Aspect 7: The femoral head arthroplasty system of any of aspect 1-3,further comprising mounting hardware, and wherein the mounting platedefines at least one opening configured to receive the mountinghardware.

Aspect 8: The femoral head arthroplasty system of aspect 7, wherein themounting hardware comprises at least one screw.

Aspect 9: The femoral head arthroplasty system of any of aspect 1-3,wherein the femoral prosthesis comprises a porous or textured metal.

Aspect 10: The femoral head arthroplasty system of aspect 9, wherein theporous or textured metal is at least one metal selected from the groupconsisting of cobalt chromium, titanium, and tantalum.

Aspect 11: The femoral head arthroplasty system of any of aspect 1-3,wherein the femoral prosthesis comprises a coating.

Aspect 12: The femoral head arthroplasty system of aspect 11, whereinthe coating is one selected from the group consisting of hydroxyapatite,titanium oxide, titanium nitride, zirconium oxide, and pyrolytic carbon.

Aspect 13: The femoral head arthroplasty system of aspect 11, whereinthe coating is configured to promote ingrowth or on-growth of bone.

Aspect 14: The femoral head arthroplasty system of any of aspect 1-3,wherein the diameter of at least a portion of the implant body rangesfrom about 10 mm to about 18 mm.

Aspect 15: The femoral head arthroplasty system of any of aspect 1-3,wherein the implant body has a variable outer diameter.

Aspect 16: The femoral head arthroplasty system of any of aspect 1-2,wherein the adapter has a Morse taper.

Aspect 17: The femoral head arthroplasty system of any of aspect 1-2,wherein the femoral head replacement is angularly offset from thefemoral prosthesis.

Aspect 18: A method comprising: forming a prepared site within a femur;and implanting a femoral head arthroplasty system according to any oneof aspect 1-17 such that the implant body is received within theprepared site, wherein the prepared site extends no more than 30 mmdistal to the lesser trochanter of the femur.

Aspect 19: The method of aspect 18, wherein the mounting plate has amajor dimension that is greater than or equal to a major radialdimension of the femur, and wherein the mounting plate abuts corticalbone at a cut proximal end of the femur.

Aspect 20: A kit comprising: a femoral prosthesis comprising: a mountingplate having a first side and an opposed second side, an adapterextending from the second side of the mounting plate, and an implantbody extending from the first side of the mounting plate, wherein theimplant body extends from the mounting plate by a distance no greaterthan 90 mm; and a plurality of femoral head replacements, each femoralhead replacement having a generally spherical surface and comprising arecess that is shaped to complementarily receive the adapter of thefemoral prosthesis, wherein each femoral head replacement of theplurality of femoral head replacements differs from every other femoralhead replacement of the plurality of femoral head replacements in sizeor material.

Although the foregoing invention has been described in some detail byway of illustration and example for purposes of clarity ofunderstanding, certain changes and modifications may be practiced withinthe scope of the appended claims.

What is claimed is:
 1. A femoral head arthroplasty system comprising: afemoral prosthesis comprising: a mounting plate having a first side andan opposed second side, and an implant body extending from the firstside of the mounting plate, wherein the implant body extends from themounting plate by a distance no greater than 90 mm; and a femoral headreplacement having a generally spherical surface, wherein one of thefemoral prosthesis and the femoral head comprises an adapter, andwherein the other of the femoral prosthesis and the femoral head definesa recess that is complimentarily shaped to receive the adapter.
 2. Thefemoral head arthroplasty system of claim 1, wherein the femoralprosthesis comprises the adapter, wherein the adapter extends from thesecond side of the mounting plate.
 3. The femoral head arthroplastysystem of claim 1, wherein the mounting plate and the implant bodycooperate to define the recess, wherein the adapter extends distallyfrom the generally spherical portion of the femoral head replacement. 4.The femoral head arthroplasty system of claim 1, wherein the implantbody comprises at least one radially extending spline.
 5. The femoralhead arthroplasty system of claim 4, wherein the implant body comprisesa plurality of radially extending splines.
 6. The femoral headarthroplasty system of claim 1, wherein the implant body defines agenerally hemicylindrical surface.
 7. The femoral head arthroplastysystem of claim 1, further comprising mounting hardware, and wherein themounting plate defines at least one opening configured to receive themounting hardware.
 8. The femoral head arthroplasty system of claim 7,wherein the mounting hardware comprises at least one screw.
 9. Thefemoral head arthroplasty system of claim 8, wherein the at least onescrew comprises a head and a body, wherein the head of the at least onescrew defines a first thread, wherein the body of the at least one screwdefines a second thread, wherein the mounting plate defines a threadedhole that is configured for complimentary receipt of the first thread ofthe head of the at least one screw.
 10. The femoral head arthroplastysystem of claim 1, wherein the femoral prosthesis comprises a porous ortextured metal.
 11. The femoral head arthroplasty system of claim 10,wherein the porous or textured metal is at least one metal selected fromthe group consisting of cobalt chromium, titanium, and tantalum.
 12. Thefemoral head arthroplasty system of claim 1, wherein the femoralprosthesis comprises a coating.
 13. The femoral head arthroplasty systemof claim 12, wherein the coating is one selected from the groupconsisting of hydroxyapatite, titanium oxide, titanium nitride,zirconium oxide, and pyrolytic carbon.
 14. The femoral head arthroplastysystem of claim 12, wherein the coating is configured to promoteingrowth or on-growth of bone.
 15. The femoral head arthroplasty systemof claim 1, wherein the diameter of at least a portion of the implantbody ranges from about 10 mm to about 18 mm.
 16. The femoral headarthroplasty system of claims 1, wherein the implant body has a variableouter diameter.
 17. The femoral head arthroplasty system of claim 1,wherein the adapter has a Morse taper.
 18. The femoral head arthroplastysystem of claim 1, wherein the femoral head replacement is angularlyoffset from the femoral prosthesis.
 19. The femoral head arthroplastysystem of claim 1, wherein the implant body has a distal end, whereinthe distal end of the body defines a surface that extends generallyparallel to the mounting plate.
 20. A method comprising: forming aprepared site within a femur; and implanting a femoral head arthroplastysystem such that an implant body of the femoral head arthroplasty systemis received within the prepared site, the femoral head arthroplastysystem comprising: a femoral prosthesis having: a mounting plate havinga first side and an opposed second side, and the implant body, whereinthe implant body extends from the first side of the mounting plate,wherein the implant body extends from the mounting plate by a distanceno greater than 90 mm; and a femoral head replacement having a generallyspherical surface, wherein one of the femoral prosthesis and the femoralhead comprises an adapter, and wherein the other of the femoralprosthesis and the femoral head defines a recess that is complementarilyshaped to receive the adapter, and wherein the prepared site extends nomore than 30 mm distal to the lesser trochanter of the femur.
 21. Themethod of claim 20, wherein the mounting plate has a major dimensionthat is greater than or equal to a major radial dimension of the femur,and wherein the mounting plate abuts cortical bone at a cut proximal endof the femur.
 22. A kit comprising: a femoral prosthesis comprising: amounting plate having a first side and an opposed second side, anadapter extending from the second side of the mounting plate, and animplant body extending from the first side of the mounting plate,wherein the implant body extends from the mounting plate by a distanceno greater than 90 mm; and a plurality of femoral head replacements,each femoral head replacement having a generally spherical surface andcomprising a recess that is shaped to complementarily receive theadapter of the femoral prosthesis, wherein each femoral head replacementof the plurality of femoral head replacements differs from every otherfemoral head replacement of the plurality of femoral head replacementsin size or material.